Insulator supporting pin and cob



April 15, 1952 D. c. HUBBARD 2,592,698

INSULATOR SUPPORTING PIN AND COB Filed April 10, 1948 Patented Apr. 15, 1952 INSULATOR SUPPORTING PIN AND COB David C. Hubbard, Centralia, Mo., assignor to A. B. Chance Company, Centralia, Mo., a corporation of Missouri Application April 10, 1948, Serial No. 20,179

. 2 Claims.

The present invention relates to insulator supporting pins and cobs, and is particularly concerned with the provision of improved forms of pins and cobs by means of which one may eliminate the use of lead, now used for cobs, and of which there is a critical shortage.

One of the objects of the invention is the provision of an improved construction of insulator supporting pins and cobs by means of which the lead, which is now being used for cobs on steel pins, may be eliminated and improved structure provided which has marked advantages over'the prior art.

Another object of the invention is the provision of an improved insulator supporting structure comprising a steel pin, which may be of the type used for steel cross arms, wooden cross arms, or pole ends, and which is adapted to be used with a cob constructed of asuitable modern plastic, which is adapted to be secured tightly to the pin and to the insulator, when the insulator is driven home on the cob.

Another object of the invention is the provision of an improved removable cob for steel insulator supporting pins, which is adapted to be made of any one of a class of modern plastics, the electrical conducting characteristics of which may be suitably modified so as to provide a static drain for the charge, which might otherwise accumulate on the inside of the insulator, thus removing a possible source of radio interference.

Another object of the invention is the provision of an improved removable cob for the steel insulator pins used to support insulators on telephone and transmission lines, which is simple in construction, and which is provided with anchoring formations having a suitable clearance with complementary anchoring formations on the pin so that the cob can be forced on the pin, and also having the characteristic of being deformed and brought into tight engagement with the anchoring formations on the pin when the insulator is threaded on the cob.

Another object of the invention is the provision of removable and attachable cobs for steel insulator supporting pins which are tough and strong, of suitable insulating characteristics, noninflammable, capable of being roughly handled or subjected to some abuse without substantial damage, capable of economical manufacture, and adapted to be made as a unit apart from the pin so that it will not be necessary to fabricate the pins and ship them to the plant which molds cobs, as is necessary when the cobs are molded on the ends of the pins.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the single sheet of drawings accompanying the specification:

Fig. 1 is a fragmentary side elevational view showing a. fragment of an insulator and a steel pin equipped with a cob embodying the invention, the cob being shown in elevation;

Fig. 2 is a modification showing a split type of cob in connection with a steel pin, the cob being applicable to the pin in the split condition, and being brought into tight engagement with the pin by the insulator, which draws the split parts of the cob together on the anchoring formations of the pin;

Fig. 3 is an axial sectional view taken through the cob of Fig. 2 on a plane passing through the anchoring cavities;

Fig. 4 is a fnagmentary elevational view of the end of a steel pin of the type adapted to be used with the cob of Fig. 3;

Fig. 5 is a fragmentary side elevational view of the pin of Fig. 4;

Fig. 5 is a horizontal sectional view taken on the plane of the line 6-6 of Fig. 4, looking in the direction of the arrows;

Fig. '7 is a top plan view of the cob and pin of Fig. 8;

Fig. 8 is a fragmentary side elevational view of the top end of a modified form of pin;

Fig. 9 is a top plan view of the modified pin of Fig. 8.

The cobs embodying the present invention are preferably made out of a suitable plastic, such as polyethelyne, cellulose acetate butyrate, polyvinyl chloride, nylon, or the like; and the preferred plastic material is cellulose acetate butyrate on account of its cheapness and plentiful supply.

In order to prevent a static charge being built up on the under side of the insulator, due to the different dielectric properties of the insulator and the cob, the electrical conducting characteristics of the plastic are preferably modified by incorporating an electrical conducting material, such .as carbon dust; or the plastic may be coated or painted with a conductive paint coating of similar material.

Referring to Fig. 1, It! indicates an electrical insulator which is mounted upon a cob H carried by a steel pin l2. The lower part of the steel pin l2 may be substantially the same as the steel pins of the prior art, which are provided with a noncircular wrench-engaging portion, an annular skirt, and a reduced cylindrical threaded end portion having a nut (not shown).

The steel pin i2 may have its upper end provided with threads similar in size and shape to the threads usually employed upon wooden pins, and complementary to the threads on the inside of the cob H, as indicated by dotted lines at 35 in Figure 1. These threads 31, on the pin [2, engaging the threads 36 on the inside of the cob H, may be regarded as one form of anchoring formations.

Referring now to Figure 7, the steel pin I2 may, in this modification, have its upper cylindrical end is provided with a plurality of radially projecting and longitudinally extending ribs it, which will be substantially V-shaped in cross-section. The ribs l4 extend from the top l5 of the pin to a point short of the end of the cob, after the cob has been applied. The size of the ribs M is preferably such that a cob with an under sized bore and grooves complementary to theribs M may be forced over the upper end [3 of the pin, the plastic cob stretching and deforming slightly.

The insulator ii] may be provided with an under sized hole is slightly tapered from the bottom to the top and provided with over sized threads l'l relative to the threads on the cob.

The size of the hole in the cob and its grooves forthe ribs id is preferably such that when the cob is forced on the end of the pin, it is held against rotation by the ribs Hi and complementary grooves H3 in the cob.

Therefore, the cob doesnot tend to rotate on the pin when the insulator is applied; and the tapered threaded bore of the insulator is adapted to compress the deformed cob as the insulator progresses downwardly on the cob until the ribs 1 H8 are firmly embedded on the inside of the cob and the cob is secured against rotation or axial movement on the pin l2.

Since the ribs M on the pin and the grooves 19 in the cob terminate short of the lower end In this case the pin 28 is reduced in size at 2 l, I

being provided with a frusto-conical portion and a reduced upper cylindrical portion 22, the upper cylindrical portion 22 having radially projecting short ribs 23, which extend longitudinally of the pin and are oppositely located.

The cob Fi l of plastic, when its split ends are brought into engagement with each other, so

that the-split 25 disappears, is of a size substantially complementary to the upper end of the pin, having a bore 23 complementary to the outer shape of the pin at 2! and 22.

At its upper end the bore has the two oppositely located grooves 2?, which are complementary in shape to theribs 23 on the pin.

The operation of this embodiment is as follows: The split 25 exem lified by two V shaped grooves extending longitudinally into the two diametrically oppositesides of the cob at 25. This spreads the skirts of the cob 2 3 sufficiently so that the lower corner 23 of the-groove 2i clears 4 the lowercorner 29 of the ribs 23 on each side of the pin.

The operator may then apply the insulator, and the cob is held against rotation by the engagement of the upper portions of the ribs 23 in the upper portions of the grooves 21. Here again the threaded bore in the insulator may be under sized and/or provided with over sized threads in relation to the threads on the tapered external part of the cob when it is compressed together.

As the insulator progresses downwardly on the threads of the cob, the two split end portions 30 and 3| will be forced together, closing the splits at 25 and drawing the grooves or recesses 21 closely about the ribs 23.

shaped ribs as and 35 on the opposite sides.

These cross ribs 35, 35 engage annular grooves in the cobs or are embedded into the cob wall to lock the cob on the pin when the insulator is installed; and the tapered under sized bore and/or over sized threads on the inside-of .the insulator tend to compress the taperedcob on the pin.

The cob in this case may be substantially. the same as the cob ll of Fig. 1 except thatit may have partially annular grooves complementary to the peripherally extending ribs 34, 35.

It will thus be observed that I have invented an improved cob for mounting insulators on steel pins, which has the following advantages:

1. The cob is detachable and replaceable-and may be manufactured apart from the steel pin.

2. The cob is self-locking on the steel pin.

3. The cob is semi-plastic, semi-conducting, and molded so that its size and proportions may be made suitable for a'steel pin or complementary external shape.

4. The shape of the steel pin is such that it may be easily forged.

5. The use of such cobs made of a modern plastic conserves lead used on steel for cobs, of which there is a critical shortage.

6. The use of the present cobs will be economical, as cellulose acetate butyrate, which is pre-- ferred, is no more expensive than lead; and this plastic is plentiful in supply.

While I have illustrated a preferred embodi clam as new and desire to secure by Letters Pat ent of the United States, is:

1. In an insulator supporting pin, the :combination of a metal pin having means foriattachment'to a cross-arm or the like, saidpin having a substantially cylindrical upper end provided with anchoring formations thereon, a separate sleeve of cellulose acetatebutyrate molded to be provided with an internal bore substantially complementary in shape to the .end oftheypin and its anchoring formations, and having on its exterior surface threaded formations complementary to those on the inside of a glass insulator, the said anchoring formations securing the sleeve on the pin When the glass insulator is driven home on the threaded formations which are provided on the exterior of the sleeve, the said sleeve being provided with a pair of diametrically opposite slits in its sides extending over the major portion of the length of the sleeve and permitting its opposite lower parts to be spread for engagement over the pin with its anchoring formations, the application of the insulator to the external threads of the sleeve causing the slits to close and the side portions of the sleeve to approach each other, to clamp the anchoring formations more firmly.

2. In an insulator supporting pin, the combination of a metal pin having means for attachment to a cross-arm or the like, said pin having a substantially cylindrical upper end provided with anchoring formations thereon, a separate sleeve of cellulose acetate butyrate molded to be provided with an internal bore substantially complementary in shape to the end of the pin and its anchoring formations, and having on its exterior surface threaded formations complementary to those on the inside of a glass insulator, the said anchoring formations securing the sleeve on the pin when the glass insulator is driven home on the threaded formations which are provided on the exterior of the sleeve, the said sleeve being provided with a pair of diametrically opposite slits in its sides extending over the major portion of the length of the sleeve and permitting its opposite lower parts to be spread for engagement over the pin with its anchoring formations, the application of the insulator to the external threads of the sleeve causing the slits to close and the side portions of the sleeve to approach each other, to clamp the anchoring formations more firmly, the said anchoring formations comprising threads formed on the pin which are complementary to internal threads formed on the inside of the sleeve.

DAVID C. HUBBARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 268,075 Brown Nov. 28, 1882 875,902 Egener Jan. 7, 1908 1,122,030 Sandford Dec. 22, 1914 2,297,600 Williams Sept. 29, 1942 FOREIGN PATENTS Number Country Date 356,299 Germany July 25, 1922 

